keel bolt sealant characteristics

[Rum Run]

Just a quick question: should the sealant around a keel bolt (or stud) where it goes through the GRP hull be non-hardening?
Specifically the sealant I am considering is a butyl rubber mastic which skins enough to be painted (which I shall not be doing, but the blurb says it does it) but does not harden ever.
Thanks in advance

 

[Graham376]

Don't know about other manufacturers but Moody use a none hardening 2 part butyl rubber compound on the tops of the keels. Inside the hull, it's normal to place a donut of caulking cotton around the studs, some info here - Curing leaking keel bolts (craigmarine.info)

 

[pvb]

Bavaria attach the keel with Plexus MA310, a high strength 2-part methacrylate adhesive designed for structural bonding of thermoplastic, metal, and composite assemblies. It sets hard, with no elasticity, in an hour, and the nuts on the keel bolts can then be torqued up.

There's an interesting Bavaria manual showing how to attach the keel, see here - http://bavariayacht.org/forum/index.php?action=dlattach;topic=3026.0;attach=5303

 

[Tranona]

Just a quick question: should the sealant around a keel bolt (or stud) where it goes through the GRP hull be non-hardening?
Specifically the sealant I am considering is a butyl rubber mastic which skins enough to be painted (which I shall not be doing, but the blurb says it does it) but does not harden ever.
Thanks in advance

Are you attaching a keel from scratch, replacing a bolt or just sealing a nut? There is no one way of dealing with keels and bolts nor one sealant. pvb describes the Bavaria method, which is similar to other builders of modern high aspect ratio keels. At the other extreme when I refitted the long cast iron keel to my wooden boat I used the traditional method of a canvas strip bedded either side in non setting Boat Life, a polysulphide. The Moody method is somewhere in between reflecting the period when they were built and the design of the keel.

So, helpful to know what you are actually planning to do.

 

[Rum Run]

The boat has a fairly low aspect cast iron fin held on with IIRC 12 off 7/8"BSW studs and nuts. The nuts are all pretty rusty so the intention is to remove them one at a time, rake out any sealant if it looks stained by rust, inspect the thread on the stud, replace if necessary then reseal the gap between the hole and the stud. The mild steel plates under the nuts are pretty rusty too so they will be replaced.
The boat dates from 1968, 31' long, does not leak at the keel/ hull line and I am not intending to rebed the keel. Tbh the one stud I pulled looks serviceable, though it is basically all-thread not actually a stud, which doesn't seem optimal but hey ho!

 

[Rum Run]

Don't know about other manufacturers but Moody use a none hardening 2 part butyl rubber compound on the tops of the keels. Inside the hull, it's normal to place a donut of caulking cotton around the studs, some info here - Curing leaking keel bolts (craigmarine.info)

Interesting stuff in the link.
I note that they are using stainless nuts on stainless studs but do not mention copperslip or some other preventer of galling on the threads

 

[Tranona]

The boat has a fairly low aspect cast iron fin held on with IIRC 12 off 7/8"BSW studs and nuts. The nuts are all pretty rusty so the intention is to remove them one at a time, rake out any sealant if it looks stained by rust, inspect the thread on the stud, replace if necessary then reseal the gap between the hole and the stud. The mild steel plates under the nuts are pretty rusty too so they will be replaced.
The boat dates from 1968, 31' long, does not leak at the keel/ hull line and I am not intending to rebed the keel. Tbh the one stud I pulled looks serviceable, though it is basically all-thread not actually a stud, which doesn't seem optimal but hey ho!

Ring of caulking cotton in the gap and polysulphide (Arbokol) would be my choice.

Stainless on stainless is normal for production boats. Worst that can happen is that the studs might unscrew when the nut is being removed. Most modern boats never need the keel bolts touching throughout their lives.

 

[Keith 66]

Butyl rubber is said to be non hardening, it isnt, the butyl rubber my windows were assembled with has gone hard ten years after they were made & now i will have to strip & re seal them as they have started to leak. These were new ally / glass windows from a reputable british manufacturer.
It is not the material for sealing keels I would use a two part polysulphide like Arbokol.